Head drum apparatus

Abstract

A head drum apparatus includes a cylindrical piezoelectric ceramic member formed of a polarized ceramic material and having inner and outer peripheral surfaces. A plurality of electrodes are formed on at least one of the inner and outer peripheral surfaces of the piezoelectric ceramic member. The piezoelectric ceramic member vibrates in response to an AC voltage applied to the electrodes. A cylindrical stationary head drum having an inner peripheral surface and an outer peripheral surface around a portion of which a magnetic tape is wound is caused to vibrate in a bending mode under vibration of the piezoelectric ceramic member. The stationary head drum includes a cylindrical stationary portion, a cylindrical vibratory portion and a cylindrical thin wall portion provided between the stationary portion and the vibratory portion. The piezoelectric ceramic member is coupled to the vibratory portion so that the vibratory portion is caused to vibrate under vibration of the piezoelectric ceramic member. Tape data indicative of types of the tapes is read out for driving the piezoelectric ceramic member by the AC voltage having a frequency and an amplitude determined on the basis of the tape data.

What is claimed is: 
     
       1. A head drum apparatus, comprising: a cylindrical stationary head drum having an inner peripheral surface and an outer peripheral surface around a portion of which a magnetic tape is wound; and   a piezoelectric ceramic member coupled to said inner peripheral surface of said head drum and including a cylindrical piezoelectric ceramic material which has an inner peripheral surface and an outer peripheral surface, first electrode means formed on said inner peripheral surface of said piezoelectric ceramic material, and second electrode means formed on said outer peripheral surface of said piezoelectric ceramic material;   wherein said piezoelectric ceramic material includes at least two portions each of which is polarized by applying DC voltage between said first electrode means and said second electrode means such that adjacent ones of said portions have polarities opposite to each other, and said first electrode and said second electrode provides flexural vibration in response to AC voltage applied between said first electrode means and said second electrode means to cause said outer peripheral surface of said head drum to vibrate.   
     
     
       2. A head drum apparatus according to claim 1, further comprising: a second piezoelectric ceramic member coupled to an inner peripheral surface of said piezoelectric ceramic member and including a second cylindrical piezoelectric ceramic material which has a second inner peripheral surface and a second outer peripheral surface, third electrode means formed on said second inner peripheral surface of said second piezoelectric ceramic material, and fourth electrode means formed on said second outer peripheral surface of said second piezoelectric ceramic material;   wherein said second piezoelectric ceramic material is divided into at least two second portions each of which is polarized by applying second DC voltage between said third electrode means and said fourth electrode means such that adjacent ones of said second portions have polarities opposite to each other, and said third electrode means and said fourth electrode means provides flexural vibration in response to second AC voltage applied between said third electrode means and said fourth electrode means to cause said outer peripheral surface of said head drum to vibrate.   
     
     
       3. A head drum apparatus according to claim 1, wherein said outer peripheral surface of said head drum is formed with a plurality of small notches.   
     
     
       4. A head drum apparatus according to claim 1, wherein said head drum includes a stationary portion, a cylindrical vibratory portion to which said piezoelectric ceramic member is coupled such that said cylindrical vibratory portion is caused to vibrate in response to vibration of said piezoelectric ceramic member, and a cylindrical thin wall portion provided between said stationary portion and said cylindrical vibratory portion.   
     
     
       5. A head drum apparatus according to claim 1, wherein said piezoelectric ceramic member further includes a pair of particular electrodes one of which is formed on said inner peripheral surface of said piezoelectric ceramic material and the other of which is formed on said outer peripheral surface of said piezoelectric ceramic material; and   said head drum apparatus further comprises driving means for outputting said AC voltage, acceleration detecting means for detecting acceleration from a voltage appearing across said pair of particular electrodes, and control means for controlling a frequency of said AC voltage, which is outputted from said driving means, in accordance with the acceleration detected by said acceleration detecting means.   
     
     
       6. A head drum apparatus according to claim 5, further comprising dew detecting means for detecting dew on said outer peripheral surface of said head drum to generate a vibration start signal, and; wherein said driving means outputs said AC voltage after receiving said vibration start signal from said dew detecting means.   
     
     
       7. A head drum apparatus according to claim 5, further comprising: tape data storing means for storing tape data indicative of amplitudes and frequencies of said AC voltage in dependence on types of magnetic tapes, respectively;   detecting means for detecting a type of a magnetic tape being used; and   reading means for reading out the tape data in dependence on the detected type to generate an amplitude signal and a frequency signal in accordance with the read out tape data;   wherein said driving means outputs said AC voltage having an amplitude and a frequency which are indicated by said amplitude signal and said frequency signal, respectively.   
     
     
       8. A head drum apparatus according to claim 7, wherein said detecting means detects the type of the tape being used based on information presented by a case in which the tape being used is accommodated.   
     
     
       9. A head drum apparatus according to claim 7, wherein said detecting means detects the type of the tape being used based on predetermined values indicative of the types of the tapes.   
     
     
       10. A head drum apparatus according to claim 5, further comprising: tension data storage means for storing tension data indicative of tension to be applied to magnetic tapes; tension detecting means for detecting a tension applied to a tape being used;   means for generating an amplitude signal indicative of an amplitude determined based on the detected tension and stored tension data; and   wherein said driving means outputs said AC voltage having an amplitude which is indicated by said amplitude signal.   
     
     
       11. A head drum apparatus according to claim 5; wherein said driving means outputs said AC voltage while varying a frequency of said AC voltage within a predetermined frequency range including a resonance frequency of said stationary drum head in response to a detection start signal,   said acceleration detecting means supplies said detection start signal to said driving means to detect a maximum acceleration over a period during which the frequency of said AC voltage is varied; and   said driving means outputs said AC voltage having a frequency which is determined when said maximum acceleration is detected by said acceleration detecting means.   
     
     
       12. A head drum apparatus according to claim 1: wherein said first electrode means includes a first plurality of electrodes; and   said second electrode means includes a second plurality of electrodes each of which is formed so as to be opposite to a corresponding one of said first plurality of electrodes.   
     
     
       13. A head drum apparatus according to claim 12 wherein each of said second plurality of electrodes is formed so as to extend to said inner peripheral surface of said piezoelectric ceramic material. 
     
     
       14. A head drum apparatus according to claim 13 wherein said piezoelectric ceramic member further includes: first connection means for electrically connecting said first plurality of electrodes after polarizing said piezoelectric ceramic material; and   second connection means for electrically connecting said second plurality of electrodes after polarizing said piezoelectric ceramic material.   
     
     
       15. A head drum apparatus according to claim 12 wherein said piezoelectric ceramic member further includes: first connection means for electrically connecting said first plurality of electrodes after polarizing said piezoelectric ceramic material; and   second connection means for electrically connecting said second plurality of electrodes after polarizing said piezoelectric ceramic material.   
     
     
       16. A head drum apparatus according to claim 1 wherein one of said first electrode means and said second electrode means includes a common electrode; and   the other of said first electrode means and said second electrode means includes a plurality of electrodes.   
     
     
       17. A head drum apparatus according to claim 16 wherein said piezoelectric ceramic member further includes connection means for electrically connecting the other of said first electrode means and said second electrode means after polarizing said piezoelectric ceramic material. 
     
     
       18. A head drum apparatus according to claim 1: wherein one of said first electrode means and said second electrode means includes a common electrode and a first electrode; and   the other of said first electrode means and said second electrode means includes a plurality of electrodes one of which is formed so as to be opposite to said first electrode.   
     
     
       19. A head drum apparatus according to claim 18 wherein said piezoelectric ceramic member further includes connection means for electrically connecting said plurality of electrodes after polarizing said piezoelectric ceramic material.